A new catalyst based on the K/Ca/Ni oxide system has been developed for the oxidative coupling of methane at <700°C. It is capable of up to 70% selectivity to C2+ hydrocarbons at complete O2 conversion (CH4/O2 RATIO = 2.5) if 35% water is present in the feed. Unlike previous materials of this type, the present catalyst is stable at the conditions of its maximum yield to C2+ products and is not poisoned by CO2. On the contrary, it appears as if CO2 promotes formation of a selective hydroxycarbonate phase which develops under reaction conditions.